.cd-top {
    display: inline-block;
    height: 40px;
    width: 40px;
    position: fixed;
    bottom: 40px;
    right: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.05);
    /* image replacement properties */
    overflow: hidden;
    text-indent: 100%;
    white-space: nowrap;
    background: rgba(128, 128, 128, 0.8) url(../images/top.svg) no-repeat center 50%;
    visibility: hidden;
    opacity: 0;
    -webkit-transition: opacity .3s 0s, visibility 0s .3s;
    -moz-transition: opacity .3s 0s, visibility 0s .3s;
    transition: opacity .3s 0s, visibility 0s .3s;
}

.cd-top.cd-is-visible, .cd-top.cd-fade-out, .no-touch .cd-top:hover {
    -webkit-transition: opacity .3s 0s, visibility 0s 0s;
    -moz-transition: opacity .3s 0s, visibility 0s 0s;
    transition: opacity .3s 0s, visibility 0s 0s;
}

.cd-top.cd-is-visible {
    /* the button becomes visible */
    visibility: visible;
    opacity: 1;
}

.cd-top.cd-fade-out {
    /* if the user keeps scrolling down, the button is out of focus and becomes less visible */
    opacity: .5;
}

.no-touch .cd-top:hover {
    background-color: #808080;
    opacity: 1;
}

@media only screen and (min-width: 768px) {
    .cd-top {
        right: 20px;
        bottom: 20px;
    }
}

@media only screen and (min-width: 1024px) {
    .cd-top {
        height: 60px;
        width: 60px;
        right: 30px;
        bottom: 30px;
    }
}